You know me and my trickery, don't you! Remember that 18 billion solar masses, although an incredibly massive black hole (a solar mass is the amount of material in our own Sun), is massive in another way: it is the size of an entire galaxy! Which means that its density is actually very low!

Just thought I'd throw in an interesting, thought-provoking question (after all the cryptic stuff ).

The answer, actually, is that the centre of certain black holes in fact achieves an infinite density!! No person entering such a black hole could avoid falling into the centre, where he will be crushed into infinite density, his mass being added to that of the black hole. (Of course, he will be crushed long before he reaches the centre, in any case.)

Okay, since Bishop got closest with his cogitating logic, I hand the mantle over to him ...Bishop, you're IT!

Unfortunately, this is a hoax that began back in 2003. On August 27th, 2003, Mars closed to a distance of only 55,758,006 kilometers (34,646,418 miles), which was its closest distance from Earth within the last 50000 years or so (but only by a small amount!)

Now, because some bright spark thought it fun to let the story redo the rounds year after year, the original e-mail from 2003 that was doing the rounds then has been circulating every August thereafter - and probably will suck in gullible people every year for who knows how long!

The original e-mail went something like this:

"The Red Planet is about to be spectacular! This month and next, Earth is catching up with Mars in an encounter that will culminate in the closest approach between the two planets in recorded history. The next time Mars may come this close is in 2287. Due to the way Jupiter's gravity tugs on Mars and perturbs its orbit, astronomers can only be certain that Mars has not come this close to Earth in the Last 5,000 years, but it may be as long as 60,000 years before it happens again.The encounter will culminate on August 27th when Mars comes to within 34,649,589 miles of Earth and will be (next to the moon) the brightest object in the night sky. It will attain a magnitude of -2.9 and will appear 25.11 arc seconds wide. At a modest 75-power magnificationMars will look as large as the full moon to the naked eye. By the end of August when the two planets are closest, Mars will rise at nightfall and reach its highest point in the sky at 12:30 a.m. That's pretty convenient to see something that no human being has seen in recorded history. So, mark your calendar at the beginning of August to see Mars grow progressively brighter and brighter throughout the month. Share this with your children and grandchildren. NO ONE ALIVE TODAY WILL EVER SEE THIS AGAIN."

Now, unfortunately, the Moon only orbits the Earth at a distance of around 385,000 km (240,000 miles). Mars was close in 2003, but it was still 144 times further away than the Moon! Instead of appearing as a huge red globe the size of the moon in the sky, Mars looked like a bright red star. Now, if you use a telescope at about 75-times magnification, the size of Mars in the eyepiece would roughly appear the size of the Full Moon seen with the naked eye!

Opposition - which is when two heavenly bodies reach their closest distance from each other - happens about every 2 years or so between Mars and Earth. And it varies by date: in 2007, it happened on December 18th, and this year it has already occurred on January 29th! In 2018, the opposition will be almost as close as the 2003 event, but Mars will always only appear as a bright red star to the naked eye, not a huge red disc the size of our Moon!

If memory serves, from his star counting Herschel determined the rough shape of the solar system. No further details spring to mind. I do know he set up the NGC (New General Catalogue) system for numbering stellar objects and was the original discoverer of nebulae - but I don't think that's what you are looking for

“ Every year elephants were becoming scarcer and wilder south of the Zambezi, so that it had become impossible to make a living by hunting at all. ” FC Selous 1881

Your input is always appreciated, TP! You have some excellent memory banks there - Herschel was astronomically involved in several things. The shape of something is on the right rack, but it is not the solar system.

TP, well done! Yes, Herschel spent aeons of time counting the stars in 2000 samples of views of the skies through his telescope; from this, he deduced that a certain part had much greater density of stars than the others, which suggested that the solar system was in the middle of a giant disk. So, he was the first to discover that our galaxy is disk-shaped. However, it has subsequently been proven that the sun is nowhere near the centre of the galaxy, but towards the outer fringes of the spiral.